Transporting RAID-1 image from a 40G to a 80G set

[Mark]

Ok, I know this issue has been brought up in many variations in the past,
but I would like to know how to make a disk-image of my RAID-1, in such a
way that I can transport the image from a 40G to a 80G set (FreeBSD 4.7R).

I know I can use dd to copy the data to another blank hard disk. But I
wonder whether a hard disk with such an image can really be used as
'template' for the new 80G array. For one because I suspect the
RAID-controller (the onboard Promise 20276 RAID) actually marks the disks in
its array set (as in: writes to a specific sector, so as to know who is
who), so that I can not just swap it for another disk which, seemingly, has
the same image (made with dd). And for two, of course, because I doubt I can
get the RAID-controller to do the RAID-equivalent of a "growfs".

It may just be I have to rebuild a 80G array from scratch. But still then
the same problem exists: how to restore the root-partition onto the new
array? The normal procedure would be to place an extra blank disk, onto
which I would restore a dump-file, after which I cable the extra disk to be
the primary disk again; but that would bring the same issue as above: such
an extra disk cannot take the place of one of the disks in the array (as the
RAID-controller marks those).

So, has anyone any ideas?

- Mark